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Tysabri's been REWORKED now so that there is only a 1 in 1000 chance of getting a serious viral infection of the brain. Ho ho ho.

The worthlessness of this statistic that is endlessly repeated makes it almost laughable. Only here on this site have I read analyses that are meaningful, but which seem to elude almost everyone else because they are so hung up on this 1 in 1000 number. Hopefully time will show that with proper monitoring, the risk of monotherapy is even less.

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Tysabri's been REWORKED now so that there is only a 1 in 1000 chance of getting a serious viral infection of the brain. Ho ho ho.

This 1/1000 number came from the info that out of about 3000 patients that used Tysabri in various trials, 3 became infected with PML.

But on another MS site, a poster who appeared to know a lot about statistics, stated that you simply could not take those numbers and come up with the conclusion that they did...especially when it came to real statistics. He stated that several variables would have to be factored into any probability number that accurately determined what the real risk would be. Since he did not have access to these variables it was impossible to determine.

The 1/1000 appears to look nice on marketing/sales presentations but as one person commented....if a couple of hundred thousand MS patients end up on Tysabri, do the numbers and it isn't very nice!

But on another MS site, a poster who appeared to know a lot about statistics, stated that you simply could not take those numbers and come up with the conclusion that they did...especially when it came to real statistics. He stated that several variables would have to be factored into any probability number that accurately determined what the real risk would be. Since he did not have access to these variables it was impossible to determine.

I'm sure there are more complicated ways of calculating the risk, but the simple facts appear to be that 3 out of 3,000 on the trial got PML. The simple risk is 1 in 1,000. It can't be any higher unless one thinks that Biogen are hiding the number who got PML. It could be lower if some account was taken of the circumstances of those who got PML i.e. other drugs they had used etc. The real issue is that the risk was only based on the duration of the trial. We might have to wait 5-10 years before the long term risks are known (could be worse than 1 in 1,000 or better). And by then more should be known about the benefits (with which to compare against the risks). In reality there is not that much data and it is over a relatively short time period - it will be important for those considering this treatment option to consult fully with their neuro and family before making a decision.

I'm sure there are more complicated ways of calculating the risk, but the simple facts appear to be that 3 out of 3,000 on the trial got PML. The simple risk is 1 in 1,000.

That's more or less what I stated on that MS Forum as well but was sort of raked over the coals for making that comment...at least from a proper statistical point of view.

The chap did say that he couldn't give the real probability risk, either higher or lower but the 1/1000 was simply not correct based on how that number was tabulated. I certainly was not in a position to debate that with him...I had a hard enough time passing algebra and calculus in my senior year of high school

2 of the PML patients received Tysabri in combination with Avonex. Eliminate them from the risk ratio as Tysabri can only be prescribed as a monotherapy.

1 of the PML patients received Tysabri as a monotherapy, however...note: he was a Crohn's patient with a severely compromised immune system which included a past medical history of use with very strong immune suppressant medications for his CD such as azathioprine (Imuran).

Thus, the unjust1:1000 risk ratio for PML when using Tysabri, and the risk factor is probably much lower than the 1:1000 due to: "Tysabri is indicated for use as a monotherapy, meaning it should not be used in combination with other immune system modifying drugs, and is for patients who have not responded adequately to, or cannot tolerate, other treatments for MS. "

msladyinca wrote:3 patients out of 3,000 in the trials contracted PML.

Correct...but according to statistics, it is wrong to state that the probability of getting PML from using Tysabri is 1:1000. I made that assumption on the Brain Talk MS Forum and a person who was a statistician (or knew a lot about statistics) told me that was wrong when it came to statistics. He went on to say that probability depended on several variables of which were not known so the number here could be higher or even lower.

2 of the PML patients received Tysabri in combination with Avonex. Eliminate them from the risk ratio as Tysabri can only be prescribed as a monotherapy.

Shortly after Tysabri was pulled, James Mullen, the CEO of Biogen stated that Avonex had several hundred thousands patient use years behind it with no known cases of PML. So was it the combo or Tysabri all by itself. Nobody today knows the answer to that question.

1 of the PML patients received Tysabri as a monotherapy, however...note: he was a Crohn's patient with a severely compromised immune system which included a past medical history of use with very strong immune suppressant medications for his CD such as azathioprine (Imuran).

Biogen would like you to think that but this Crohn's patient had stopped using Infliximab 20 months before using Tysabri and stopped using Azathioprine 8 months before. Although he was in an earlier Tysabri clinical trial, he was on the placebo. The JCV virus appeared in his blood during the monotherapy Tysabri use between Feb - June 2003.

Thus, the unjust1:1000 risk ratio for PML when using Tysabri, and the risk factor is probably much lower than the 1:1000 due to: "Tysabri is indicated for use as a monotherapy, meaning it should not be used in combination with other immune system modifying drugs, and is for patients who have not responded adequately to, or cannot tolerate, other treatments for MS. "

Which begs the question...why was Biogen combining Tysabri with another immune system altering drug such as Avonex when they didn't even have safety data figured out for the Phase III trials of the drug by itself. One financial analyst stated it was to keep the market share of Avonex up....something that big pharma is always concerned about.

I just wish that Biogen had stuck to their original plan...Tysabri by itself, Phase III trials for two full years...analyze the data, determine the safety, get the FDA approval and THEN release the drug to the public. They gambled, took the fast route, it blew up in their face and now MS patients such as yourself are having to fight needlessly to use a drug that you desperately want to try. It simply isn't right!

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